Ok, I'm back.
There are TONS of benefits (physical and emotional) so I hope other mamas will add on to this thread. I used to have lots of links with more scientific/studied info but I let go of them long ago, so I'll just share what has stuck with me and what I have experienced.
If enough mamas respond, it'd be good to have this as a sticky for new and contemplating mamas to see.
Here's a starter...physical:
--long-lasting immunity, even with small amounts of breastmilk, and the results last a lifetime
--brain development--only human breastmilk has the properties to make sure that the human brain develops to it's fullest human potential, and even though they say this is a general benefit of breastfeeding (ie: for the first year or two or whatever) I highly doubt the benefits abruptly end (or stop working) simply because a child is over x-years
--higher intelligence (related with meeting fullest human potential...or how we were biologically meant to be)
--for mother, a decreased risk of breast cancer
--proper jaw formation
--there are no physical hazards to breastfeeding beyond x-years, breastmilk is natural and golden regardless of ageemotional:
--a wonderful start in life by having a child's innate needs trusted, honored and fulfilled
--connection and empathy (something American society is lacking) as a result
--a close trusting bond with one's mother, more likely to last a lifetime
--provides comfort and "centering/grounding" during times of stress or trauma
--provides ultimate peacefulness and good-feelings (especially important at bedtime)